This proposed Ischemic Heart Disease SCOR is a multidisciplinary laboratory and clinical research program focused on the cellular mechanisms underlying post-ischemic myocardial inflammation, emphasizing the role of the endothelium in promoting early neutrophil (PMN) targeting and possible PMN- mediated myocardial reperfusion injury. The specific objectives are to determine (1) the role of adhesion between PMNs and endothelium in post- ischemic myocardial inflammation, the changes that occur in endothelial cell expression of adhesion molecules and actin cytoskeletal organization that mediate targeting and accumulation of PMNs in reperfused myocardium, and the mechanisms responsible, including local production of proinflammatory cytokines, increases in endothelial cell cytoplasmic Ca2+ concentration, and alterations in tyrosine kinase activity associated with receptors and focal adhesion sites, (2) the role of oxygen free radicals in post-ischemic myocardial inflammation, including their role in enhanced surface expression and synthesis of PMN and endothelial adhesion molecules and activation of complement, and the cellular mechanisms responsible for free radical generation in endothelial cells and PMNs, (3) the role of endothelial-derived nitric oxide (NO) in modifying post-ischemic inflammation, the factors controlling NO production by different isoforms of nitric oxide synthase (NOS) following ischemia/reperfusion, and the mechanisms responsible for intracellular localization, genetic regulation and expression of endothelial cell NOS (4) whether therapy to inhibit PMN activation and/or adhesion to endothelial cells, given shortly before reperfusion, can produce a meaningful and permanent reduction in infarct size in rat and dog animal models, associated with improved left ventricular (LV) function and reduced I.V remodelling without a negative impact on infarct healing or susceptibility to infection, (5) whether combined NMR imaging of regional left ventricular function using radiofrequency tags and spatially localized 31P-NMR spectroscopic measurements of myocardial high energy phosphate concentrations can successfully differentiate dysfunctional necrotic and viable myocardium in patients following ischemia/reperfusion. The techniques to be utilized include molecular cloning, reverse transcriptase polymerase chain reaction (RT-PCR), in situ RT-PCR, enzyme inhibition with antisense oligonucleotides, immunohistology, immuno-electron microscopy, fluorescence microscopy, measurement of intracellular pH and Ca2+ concentration with fluorescent indicators, measurement of oxygen radicals and NO by electron paramagnetic resonance (EPR), combined nuclear magnetic resonance imaging and spatially localized 31P spectroscopy, and use of cultured cells, perfused hearts and in vivo animal models. We anticipate that this proposed SCOR program will yield fundamental information about the cellular mechanisms involved in the early stages of post-ischemic inflammation and will provide novel therapeutic approaches to reducing post-ischemic myocardial injury.